Over the past year, Jonathan Eisen’s reading habits have changed dramatically. For
most of the past 2 decades, he has kept up
with scientific literature primarily by combing PubMed, the vast trove of online biology
abstracts. But these days Eisen, an evolutionary biologist at the University of California, Davis, discovers research relevant to
his own work without even looking for it.

The insightful librarian helping keep
Eisen up to speed is Google Scholar, a
free academic search service maintained
by the California-based company. Google
Scholar has been studying Eisen closely.

It keeps track not only of his
own 300 papers and the key
words within them—Archaea,
Plasmodium, phylogenomics—
but also the 38,000 citations to
his work in published papers,
preprint abstracts, books, and
even conference posters. Like a
scientific version of the Netflix
movie recommendation engine,
Google Scholar scours the Internet,
scoring all scientific documents for
their predicted interest to Eisen,
and then sends him a weekly e-mail
of recommended reading.

Eisen is part of growing crowd
of converts. “Google Scholar
is having a great impact on
the research-seeking behavior
of researchers,” says Nicolás
Robinson-Garcia, a bibliometric
researcher at the University of
Granada in Spain. Robinson-Garcia claims that Google Scholar’s
compendium of articles is at least
as comprehensive as the leading
commercial academic search
databases—Thomson Reuters’ Web
of Science and Elsevier’s Scopus—and for
many disciplines in the social sciences and
humanities, even better. And by all accounts,
it is gobbling up market share. “Google is
the dominant referral source for online
journal articles, far surpassing the amount
of traffic driven by other discovery tools,”
says David Crotty, senior editor at Oxford
University Press in New York City.

But researchers aren’t just using GoogleScholar as a search engine. Its algorithmprovides citation metrics that quantifythe impact of their own published work,and these numbers are becoming part of astandard scientific CV. This byproduct ofGoogle Scholar has sparked a new concern:Because it includes sources from across theInternet—not only vetted journals—andhas no human curators, Google Scholar’scitation metric can be easily gamed.

Robinson-Garcia is part of a team that
demonstrated that vulnerability by placing
six fake papers with long lists of citations
to their own work on a webpage within the
University of Granada Internet domain.
Google Scholar’s algorithm dutifully tallied
them as real citations and in a matter of weeks,
their Google Scholar citation scores rose
significantly. The team’s findings appeared

online on 11 November in the Journal of the
American Society for Information Science
and Technology.

If Google Scholar were to provide a
breakdown of the sources it tapped for its
citation metric, Robinson-Garcia says, “our
fraud could have been easily detected.” That
lack of transparency is a deal breaker for
some bibliometric researchers, including
Rodrigo Costas Comesaña of Leiden
University in the Netherlands; he calls
Google Scholar “an unmanageable tool” for
citation analysis.

Google counters that critics areoverstating the problem. Anurag Acharya,a co-founder of Google Scholar who leadsits development, labels efforts to skew thecitation metric as “spam.” So far, he says, “thelevel of spam in scholarly articles remainslow.” Acharya chalks this up to the “largepenalty that would come with being caught”rigging the system in scholarly communities.But if social norms fail to keep academiccheaters in check, he says, “we can and willadjust the level of spam-handling.” However,he says, Google has no intention of revealingits algorithm, in part because it is tied up withthe company’s core search engine.

Google Scholar’s ascendance maysoon be challenged. “Microsoft is stillworking in this area too,”says Anne-Wil Harzing,the creator of Publish orPerish, a citation analysistool that uses data fromGoogle Scholar. A servicecalled Microsoft AcademicSearch is expanding rapidly tocover all academic domains.Meanwhile, Thomson Reutersand Elsevier have a strongfinancial incentive to keeptheir services competitive.Many universities are boundby nondisclosure agreements,but Cornell University librarianJohn Saylor says his institutionpays $155,000 per year for accessto Web of Science. As Harzingsays, “having both Google andMicrosoft in this field will surelykeep Thomson Reuters and Elsevieron their toes!”Experts say the competition hasanother benefit: giving scientistsoptions, so that they don’t come todepend on just one service, such as

Google Scholar, that may be vulnerable to
corporate downsizing. There are “persistent
rumors that Google is de-emphasizing or
even dismantling the Scholar team,” says
John Sack, founding director of High Wire,
an online publishing platform for more than
1300 journals, including Science.

Although Google Scholar generates no
direct income, Acharya is upbeat about its
future. While he declines to reveal usage
figures, he claims that the number of users
is growing worldwide, particularly in China.
And the Google Scholar team is expanding,
not contracting, he says. “Rumors of our
demise are greatly exaggerated.”